The encystment of free-living amoebas has relevance to the pathogenesis of human diseases caused by tissue invading free-living amoebas. The formation of cysts of Acanthamoeba castellanii under conditions of starvation has been chosen as a model. As cAMP appears to be involved in the process it is proposed to examine the effects of preincubation with cAMP on cellular RNA metabolism and protein kinase activity during encystment. Additionally in this regard the ability of theophylline to inhibit phagocytosis and to induce encystment will be investigated to determine if these effects are related. Glucolipids formed from UDP-(C14)-glucose will be investigated with respect to their nature and whether polyprenol types are involved. The glucolipids formed by the trophozoites will be compared with those formed during encystment. The functions of these glycolipids will be investigated to see whether they are intermediates for glycoprotein and/or cellulose synthesis.